Caption: Stigonema algae. Light micrograph of filaments of the blue-green algae Stigonema ocellatum. The name "Stigonema" translates from latin:"stigon" meaning "dotted" and "nema" meaning "thread". Here, the thread-like filaments appear dotted with rows of cells. The filaments are enclosed in a gelatinous protective sheath, and growth occurs at the tip of each branching filament. Blue-green algae (group: Cyanophyta) are considered to be one of the most primitive organisms, dating back to pre-Cambrian times. Stigonema is a filamentous blue-green algae found on, among other places, dripping rock surfaces and waterfalls. Magnification: x60 at 35mm size.